Cryptimeleon on Android

This repository is an example of how to use the cryptimeleon libraries on android. We therefore implement the Pointcheval-Sanders signature scheme from the pairing tutorial.

How to use cryptimeleon on android

1. Create a new android project in Android Studio.
   
2. Add cryptimeleon dependencies to app/build.gradle:

   implementation 'org.cryptimeleon:math:3.+'
   implementation 'org.cryptimeleon:craco:3.+'
   

   You can find details on the maven pages: math, craco

Note: When running using a Virtual Device (Android Emulator), make sure to use a x86_64 image.

Faster pairings with mcl

We use the C++ library herumi/mcl as a fast implementation of the BarretoNaehrig group. This provides a massive speedup compared to the Java implementation.

Precompiled library

We provide a precompiled version of mcljava for different architectures at app/src/main/jniLibs. To use them, you need to load the library with the System.loadLibrary("mcljava") command. By adding the dependency implementation 'org.cryptimeleon:mclwrap:3.0.0' to the inner build.gradle, you get access to the MclBilinearGroup.

Compile MCL for android

This needs to be compiled using NDK and added to the project as a jniLib.

1. Install NDK
2. Checkout MCL with the correct version (currently v1.28, which is the first release with native android support)
3. Build mcl (might not be necessary) by following the instructions
4. Build mcl for android: Go to mcl/ffi/java/android/jni and call ndk-build (either add ndk-build to your path, or use an absolute path, e.g. $<path-to-mcl>/ffi/java/android/jni$ ~/Android/Sdk/ndk/22.1.7171670/ndk-build). Currently, mcl's Application.mk builds native libraries for the arm64-v8a, armeabi-v7a and x86_64 architectures. If you require additional architectures (e.g. x86 for the Android emulator), add a space and the architecture name at the and of the line starting with APP_ABI in Application.mk before invoking ndk-build
5. Copy the directories in mcl/ffi/java/android/libs (which contain the libmcljava.so file) to app/src/main/jniLibs
6. Load mcl in the app prior usage with System.loadLibrary("mcljava"), e.g. in MainActivity.onCreate.
7. Add the dependency implementation 'org.cryptimeleon:mclwrap:3.0.0' to the app's build.gradle